Meet the American Boas

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If I say “boa,” you probably picture the tropical rain forests of South America, where the poster boy of the Boidae family, Boa constrictor, slithers through the brush. Your mind probably doesn’t leap to Los Angeles County or Colorado’s desert, but you’ll find boas there, too. The United States actually has two native boa species, the rubber boa (Charina bottae) and the rosy boa (Lichanura trivirgata), above. Their combined ranges cover much of the American west, from southern California up to Washington state, and from the Pacific coast east into Colorado, Wyoming, and Montana. The rubber boa even crosses the Canadian border into British Columbia, making it the most northerly member of the family. 

Rubber and rosy boas are smaller than their Central and South American cousins, usually growing no longer than 3 or 4 feet (Boa constrictor can reach up to 13 feet) and only as wide around as a golf ball. They’re also slower and more docile than the other members of the family. Rather than hissing and striking when confronted by larger predators or humans, they’ll roll themselves into tight balls, with their head protected in the center. Sometimes the rubber boa will also try to confuse its attacker by striking out with its blunt tail to further draw attention from its head and body. 

While not as impressive in size or ferocity, the American boas are formidable hunters, and kill their prey using the same method as other boas: constriction. Hunting at night when small mammals like mice, rats, shrews and voles are more active, the American boas lie in wait and then ambush prey when it gets too close. Striking quickly, they secure their meal with sharp, tiny teeth, curl around it and squeeze until it suffocates. While hunting, the rubber boa again makes use of its tail as a decoy. It slithers into rodent burrows and offers its tail to any protective parent that tries to attack while leaving the head free to consume the nesting young. 

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October 1, 2013 - 1:00pm
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